Analytical constraints on bimetric gravity

TL;DR

This paper derives analytical constraints on the parameter space of ghost-free bimetric gravity, ruling out many models while identifying viable cosmological solutions that explain accelerated expansion without a cosmological constant.

Contribution

It provides the first analytical constraints on bimetric gravity parameters, ensuring viable screening mechanisms and nonsingular cosmological evolution.

Findings

Four parameter directions approach general relativity

Many models are ruled out by analytical constraints

Accelerated expansion can be explained without a cosmological constant

Abstract

Ghost-free bimetric gravity is an extension of general relativity, featuring a massive spin-2 field coupled to gravity. We parameterize the theory with a set of observables having specific physical interpretations. For the background cosmology and the static, spherically symmetric solutions (for example approximating the gravitational potential of the solar system), there are four directions in the parameter space in which general relativity is approached. Requiring that there is a working screening mechanism and a nonsingular evolution of the Universe, we place analytical constraints on the parameter space which rule out many of the models studied in the literature. Cosmological solutions where the accelerated expansion of the Universe is explained by the dynamical interaction of the massive spin-2 field rather than by a cosmological constant, are still viable.